Many dump trucks are equipped with what are known as two-line dump pumps, wherein a first line is connected from a pump to a sump, and a second line is connected from the pump to a single-acting, telescopic, hydraulic cylinder. These arrangements do not include a filter, resulting in contaminated hydraulic fluid which, if not changed with relative frequency, shortens the life of the pump and the hydraulic cylinder. Apparently, with two line pumps used in dump trucks, it is not feasible to filter hydraulic fluid as the fluid is pumped, so filtering is not performed.
The prior art does not address the problem of filtering hydraulic fluid in two-line dump truck arrangements. U.S. Pat. No. 4,322,290 to Carl discloses a filter in which the reverse flow bypasses a filter element; however, Carl does not suggest an arrangement wherein hydraulic oil need not be filtered while it is pumped and, therefore, does not suggest a solution to the problem of filtering hydraulic fluid used in two-line dump pumps.
U.S. Pat. No. 3,289,841 to Quinting discloses an arrangement for filtering fluid flowing in both directions through a filter, while U.S. Pat. No. 3,190,445 to Rosaen utilizes a pair of filters to filter fluid flowing in both directions. Both Quinting and Rosaen suggest filtering hydraulic fluid while the fluid is being pumped. U.S. Pat. No. 3,322,281 to Gulick discloses an arrangement which ensures that fluid flow is always in the same direction through a filter but does not suggest that hydraulic fluid need not be filtered while it is being pumped.
In view of the aforementioned considerations, there is a need for an arrangement for filtering hydraulic fluid utilized in two-line dump truck configurations.